1. Field of the Invention
The present invention relates to a magnetoresistive head, a method of fabricating the same and a magnetic recording apparatus and, more particularly, to a magnetoresistive head formed as a laminated structure of a magnetic layer and a nonmagnetic metal layer including a silver film and used for converting a change in the magnetic field into a change of the resistivity of the device, a method of fabricating the same, and a magnetic recording apparatus employing the magnetoresistive head.
2. Description of the Prior Art
A magnetoresistive head, for example, a spin valve magnetoresistive head, a giant magnetoresistive head or the like, has been used in a magnetic sensor, a magnetic head or the like, and particularly it has been expected to attain miniaturization and large capacity of a magnetic disk device.
FIG. 1A is a sectional view showing a conventional spin valve magnetoresistive head, and FIG. 1B is a perspective view showing the conventional spin valve magnetoresistive head in FIG. 1A.
This magnetoresistive head has been so formed that, on a substrate 11, a backing layer 12, a first magnetic layer 13a, a nonmagnetic metal layer 14, and a second magnetic layer 13b, an antiferromagnetic layer (biasing magnetic layer) 15, and a protection layer 16 are formed in that order, and terminals 17a and 17b are in contact with both ends of the protection layer 16. Basic structure and operation of the spin valve magnetoresistive head have been disclosed in Patent Application Publication (KOKAI) 4-358310.
A spin valve magnetoresistance effect is defined as such phenomenon that an angle between the directions of magnetization of the first and second magnetic layers 13a and 13b is affected by the magnetic field and thus electric resistance of the spin valve film changes based on change in the above angle. By supplying constant current between the terminals 17a and 17b, such change in the electric resistance can be detected as a voltage change between the terminals 17a and 17b.
A magnitude of the spin valve magnetoresistance effect depends upon a film thickness of the nonmagnetic metal layer 14, and it may increase as the nonmagnetic metal layer 14 is formed thin and may decrease as the nonmagnetic metal layer 14 is formed thick. In other words, if the nonmagnetic metal layer 14 is formed thin, electric current passing through the nonmagnetic metal layer 14 is increased. As a result, the same magnetoresistance effect as that derived from the conventional anisotropic magnetoresistance effect is caused. Thus, in order to achieve the spin valve magnetoresistance effect (which is in general larger than the conventional anisotropic magnetoresistance effect), the thin nonmagnetic metal layer 14 is required. It is preferable to form the film thickness of the nonmagnetic metal layer 14 within a range of about 16 to 40 .ANG..
Conventionally, copper (Cu) may be used as the non-magnetic metal layer 14. Since Cu has a solid solution relation to Ni, Fe, Co and their alloys used as the magnetic layer, it can diffuse into the magnetic layer by heating. Consequently, there has been a problem in that the spin valve magnetoresistance effect on the substrate becomes small.
On the contrary, when Ag is used as the nonmagnetic metal layer 14, Ag has a non-solid solution relation to Ni, Fe, Co and their alloys used as the magnetic layer. Therefore, it may be considered that such nonmagnetic metal layer 14 has higher heat resistance than that of the conventional spin valve film using Cu as the non-magnetic metal layer 14.
However, when Ag is used as the nonmagnetic metal layer 14 and the film thickness of the Ag film is formed to be thin, the spin valve magnetoresistance effect does not occur. Thus, when the Ag film is used, the film thickness is required to be formed thick to some extent. If the Ag film is so formed, a dilemma, i.e., conflict is caused that ample spin valve magnetoresistance effect cannot be attained again.